NPR: key finder

Does anyone have one of those things that helps you find your keys? Different places sell them - like I think Brookstone, etc. I want to get somethign like this for DH, but I have read lots of reviews that say they don't really work. Anyone have one or know of one that actually works? TIA

Re: NPR: key finder

I don't know if they work, but I did see some at target yesterday. they have little stocking stuffer sections all over the store and I saw them there.